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CVE-2026-98642ModerateLocalRevised 5 Nov

bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk

MSRC advisory NVD CVE.org

Assessment

Severity
Moderate
CVSS base score
6.4CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Impact
Not stated
EPSS · 30-day forecast
No EPSS score collected
Public detection template
No Nuclei template is listed in the current collected catalog
Exploitation detected
Unknown: not stated by MSRC
Exploitability
Not assessed
Publicly disclosed
Unknown: not stated by MSRC
Customer action
Required: follow the MSRC remediation guidance
Component
Mariner
Weakness
—
Issued by
Linux
Published
20 Oct 2026 · October 2026
Last revised
5 Nov 2026Information published.
CVSS 3.1 base metricsRed raises the risk · green lowers it
Attack vector
LocalAV:L
Attack complexity
HighAC:H
Privileges required
HighPR:H
User interaction
NoneUI:N
Scope
UnchangedS:U
Confidentiality
HighC:H
Integrity
HighI:H
Availability
HighA:H

Updates that fix it

0 KBs

No KB listed

No KB update is listed in the collected MSRC record. Check the MSRC advisory for product releases and other remedies.

Affected products

Open Source Software
3 affected products
  • azl3 kernel 6.6.157.1-1 on Azure Linux 3.0
  • azl3 kernel 6.6.159.1-1 on Azure Linux 3.0
  • azl3 kernel 6.6.161.1-1 on Azure Linux 3.0

What changed

  1. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  3. Affected products: azl3 kernel 6.6.157.1-1 on Azure Linux 3.0, azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 → azl3 kernel 6.6.157.1-1 on Azure Linux 3.0, azl3 kernel 6.6.159.1-1 on Azure Linux 3.0, azl3 kernel 6.6.161.1-1 on Azure Linux 3.0
  4. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  5. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  6. Affected products: azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 → azl3 kernel 6.6.157.1-1 on Azure Linux 3.0, azl3 kernel 6.6.159.1-1 on Azure Linux 3.0
  7. Detection template: No Nuclei template listed · Customer action: Required: apply the update → Required: follow the MSRC remediation guidance · Public disclosure: No → Unknown: not stated by MSRC · Exploitation detected: Not reported by MSRC → Unknown: not stated by MSRC
  8. Detection template: Unknown: exploit-code evidence is incomplete or retained → No Nuclei template listed · CISA KEV: Unknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  9. Detection template: No Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained · CISA KEV: Not listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
Page history

Changes are dated when recorded; day views use the last saved version from that UTC day, and citations stay fixed.

Cite this version
Field-level log (38)

Up to 100 recent field edits are shown; older edits may be outside retention.

  1. 6 Nov 2026 · 17:32:22 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. 6 Nov 2026 · 17:32:22 UTC Source coverage: public-exploit-codeIncomplete → Current
  3. 6 Nov 2026 · 17:32:22 UTC Source coverage: first-epssIncomplete → Current
  4. 6 Nov 2026 · 17:32:22 UTC Source coverage: msrc-cvrfIncomplete → Current
  5. 6 Nov 2026 · 16:31:02 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  6. 6 Nov 2026 · 16:31:02 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  7. 6 Nov 2026 · 16:31:02 UTC Source coverage: first-epssCurrent → Incomplete
  8. 6 Nov 2026 · 16:31:02 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  9. 6 Nov 2026 · 09:07:49 UTC Last revised1 Nov 2026 14:49 UTC → 5 Nov 2026 14:48 UTC
  10. 6 Nov 2026 · 09:07:49 UTC Affected productsazl3 kernel 6.6.157.1-1 on Azure Linux 3.0, azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 → azl3 kernel 6.6.157.1-1 on Azure Linux 3.0, azl3 kernel 6.6.159.1-1 on Azure Linux 3.0, azl3 kernel 6.6.161.1-1 on Azure Linux 3.0
  11. 2 Nov 2026 · 17:30:39 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  12. 2 Nov 2026 · 17:30:39 UTC Source coverage: public-exploit-codeIncomplete → Current
  13. 2 Nov 2026 · 17:30:39 UTC Source coverage: first-epssIncomplete → Current
  14. 2 Nov 2026 · 17:30:39 UTC Source coverage: msrc-cvrfIncomplete → Current
  15. 2 Nov 2026 · 16:27:39 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  16. 2 Nov 2026 · 16:27:39 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  17. 2 Nov 2026 · 16:27:39 UTC Source coverage: first-epssCurrent → Incomplete
  18. 2 Nov 2026 · 16:27:39 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  19. 2 Nov 2026 · 09:04:36 UTC Last revised21 Oct 2026 18:38 UTC → 1 Nov 2026 14:49 UTC
  20. 2 Nov 2026 · 09:04:36 UTC Affected productsazl3 kernel 6.6.157.1-1 on Azure Linux 3.0 → azl3 kernel 6.6.157.1-1 on Azure Linux 3.0, azl3 kernel 6.6.159.1-1 on Azure Linux 3.0
  21. 29 Oct 2026 · 20:19:26 UTC Public detection templateNo Nuclei template listed
  22. 29 Oct 2026 · 20:19:26 UTC EPSSNot scored → No EPSS score collected
  23. 29 Oct 2026 · 20:19:26 UTC Customer actionRequired: apply the update → Required: follow the MSRC remediation guidance
  24. 29 Oct 2026 · 20:19:26 UTC Publicly disclosedNo → Unknown: not stated by MSRC
  25. 29 Oct 2026 · 20:19:26 UTC Exploitation detectedNot reported by MSRC → Unknown: not stated by MSRC
  26. 23 Oct 2026 · 09:33:49 UTC Public exploit codeUnknown: exploit-code evidence is incomplete or retained → No Nuclei template listed
  27. 23 Oct 2026 · 09:33:49 UTC CISA KEVUnknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  28. 23 Oct 2026 · 09:33:49 UTC Source coverage: public-exploit-codeIncomplete → Current
  29. 23 Oct 2026 · 09:33:49 UTC Source coverage: first-epssIncomplete → Current
  30. 23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
  31. 23 Oct 2026 · 09:33:49 UTC Source coverage: msrc-cvrfIncomplete → Current
  32. 23 Oct 2026 · 08:31:50 UTC Public exploit codeNo Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained
  33. 23 Oct 2026 · 08:31:50 UTC CISA KEVNot listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
  34. 23 Oct 2026 · 08:31:50 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  35. 23 Oct 2026 · 08:31:50 UTC Source coverage: first-epssCurrent → Incomplete
  36. 23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete
  37. 23 Oct 2026 · 08:31:50 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  38. 21 Oct 2026 · 20:45:25 UTC Last revised20 Oct 2026 01:07 UTC → 21 Oct 2026 18:38 UTC

Explore global source statements, affected packages and advisory history for CVE-2026-98642. The catalog has a separate collection scope from Microsoft release records.

Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-98642

Published

bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix UAF due to concurrent consumption of ttrace lists in alloc_bulk Syzkaller repeatedly triggered UAF splats related to nodes in waiting_for_gp_ttrace within the bpf memalloc: BUG: KASAN: slab-use-after-free in llist_del_first+0x85/0x110 lib/llist.c:61 Read of size 8 at addr ffff8881572cd080 by task syz.4.470/5112 ... llist_del_first+0x85/0x110 lib/llist.c:61 alloc_bulk+0x193/0x460 kernel/bpf/memalloc.c:229 bpf_mem_refill+0x386/0x560 kernel/bpf/memalloc.c:436 Freed by task 14: ... __free_rcu kernel/bpf/memalloc.c:281 [inline] __free_rcu_tasks_trace+0x48/0xd0 kernel/bpf/memalloc.c:291 rcu_tasks_invoke_cbs+0x1ec/0x3e0 kernel/rcu/tasks.h:571 rcu_tasks_one_gp+0x13d/0x220 kernel/rcu/tasks.h:621 rcu_tasks_kthread+0xf3/0x120 kernel/rcu/tasks.h:651 The reason is that the UAF occurs after the RCU Tasks Trace GP expires: when the __free_rcu() callback runs, there is no synchronization protecting llist_del_all() against concurrent alloc_bulk() operating on waiting_for_gp_ttrace, leading to the race condition below: CPU0 CPU1 __free_rcu (RCU Tasks Trace callback) alloc_bulk llist_del_first(&c->waiting_for_gp_ttrace) entry = smp_load_acquire(&head->first); do { if (entry == NULL) return NULL; free_all(llist_del_all(&c->waiting_for_gp_ttrace)) llist_for_each_safe(pos, t, llnode) free_one(pos); next = READ_ONCE(entry->next); <-- trigger UAF } while (!try_cmpxchg(&head->first, &entry, next)); In addition, there is also a theoretical race condition on the free_by_rcu_ttrace list. This race requires two preconditions: an in-flight Tasks Trace GP keeping c->call_rcu_ttrace_in_progress == 1, and concurrent cross-CPU frees repopulating c->free_by_rcu_ttrace with new nodes. Under these conditions, the following scenario triggers UAF: // CPU0 // irq work is still busy (on PREEMPT_RT) alloc_bulk() llist_del_first(&c->free_by_rcu_ttrace) entry = smp_load_acquire(&head->first); do { if (entry == NULL) return NULL; // CPU1 bpf_mem_alloc_destroy() WRITE_ONCE(c->draining, true) // wait for CPU0 irq_work_sync() // CPU2 do_call_rcu_ttrace(tgt(CPU0)) if (c->draining) { llist_del_all(&c->free_by_rcu_ttrace) free_all() } // CPU0 continue next = READ_ONCE(entry->next); <-- trigger UAF while (!try_cmpxchg(&head->first, &entry, next)); Fix this by introducing a raw spinlock to synchronize the concurrent consumption on waiting_for_gp_ttrace and free_by_rcu_ttrace.

Source published
18 Oct 2026 15:20:13 UTC
Source modified
19 Oct 2026 09:23:11 UTC
Observed here
23 Oct 2026 15:48:27 UTC
Source terms
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